The present invention relates to an arrangement for fixing a medical-technical measuring device to a patient""s body part, and to medical-technical measuring device having such fixing arrangement, particularly a pulsoximeter sensor.
DE 37 03 458 C2 discloses a medical-technical measuring device including arrangement fixing it a body part of a patient, particularly to a finger, a toe, an arm or a leg. A first segment of a carrier means includes a longitudinal opening extending in a longitudinal direction to receive the body part, and supports the measuring means. A second segment, adjacent the first segment, extends around the periphery and is elastic. During stressing beyond the material elasticity of the first segment, the stresses pass to the second segment. The disclosed method of manufacture involves casting around the transmitter and receiver elements, during the manufacture of the carrier means.
U.S. Pat. No. 4,685,464 discloses a clothespin-like pulsoximeter. Two arms of a clamp-like carrier means can be brought into clamping contact on the body part of the patient.
The conventional fixing arrangements and measuring devices are disadvantageous in that they include a secure fixing obtained by introduction of a higher force level and essentially pointed or clamping fixing forces, which then, for example, can lead to disturbances of the blood circulation in the body part, or in that they guarantee good blood circulation in the body part by use of reduced fixing forces, which then frequently lead to the fixing arrangement or the measuring device becoming detached from the body part, particularly upon displacement of the body part. This latter arrangement can be an important disadvantage, particularly when it is used for infants or small children and for intensive care medicine. Also, the conventional devices are costly to manufacture and require a high degree of precision and high level of skill with their use.
The present invention involves an arrangement for fixing a medical-technical measuring device to the body as well as a medical-technical measuring device, which overcome the disadvantages of conventional arrangements and devices. Particularly, the present invention ensures a secure fixing, while preventing any disturbances of the blood circulation of the body part of the patient. In addition, the fixing arrangement and measuring device can be manufactured at low cost, and are to be simple to use and to clean.
In pulsoximetry, the oxygen content of the blood of a patient is determined. Preferably, a body part with good blood circulation is exposed to rays or even irradiated with light, for example, of two different wave lengths. The relative oxygen saturation of the blood is calculated from the absorption and/or reflection. Suitable body parts for this type of measuring are, for example, the ear and the nose separating wall, but particularly the extremities such as the fingers or toes. For such medical-technical measuring device, at least one optical transmitter element and at least one optical receiver element are preferably arranged on opposite sides of the body part. On the one hand, the blood circulation of the body part is not to be obstructed. On the other hand, the elements are to be sufficiently secured in their position relative to one another, particularly in their axial alignment, so that the measuring process is not at all negatively influenced even with frequent movements of the body part, for example in the case of infants and/or of intensive care patients.
The arrangement for fixing a medical-technical measuring device according to the present invention has carrier means including a foam part. At least on the surface of the carrier means turned toward or facing the body part, the carrier means is slightly elastically deformable to obtain the fixing. The deformation makes available a force-accumulating arrangement which brings about the fixing, so that a secure fixing is attained with essentially unimpaired blood circulation of the body part. Preferably, the foam of the carrier means completely surrounds the body part, conducting the fixing force over the entire surface of the body part, and particularly is configured as a sheathing or in cap-like configuration. The exterior surface of the carrier means and the interior surface formed by the longitudinal opening can be configured as cylindrical, conical or frustoconical. With the introduction of the body part into the longitudinal opening or the slipping of the carrier means over the body part, deformation of the foam occurs particularly in radial direction in relation to the longitudinal direction. The foam material thus has the advantageous property that it can be pressed together on one fragment of its volume, and thus, makes available a permanent force-accumulation arrangement.
The term xe2x80x9cfoam materialxe2x80x9d is not intended to mean the original material forming the foam, but rather is intended to mean the solid foam product itself, in other words the synthetically produced material of cellular structure. Among other things, rubber, a rubber-plastic mixture and particularly a synthetic resin or plastic can be considered as the raw material to make the foam material. Some synthetic foam materials, which can be used, are cited in Neumuller, Otto-Albrecht: Rompp Chemie-Lexikon, Stuttgart, Francksche Verlagsanstalt [Publisher], 8th Edition, page 3703, under the key word xe2x80x9cSchaumkunststoffexe2x80x9d [xe2x80x9cSynthetic foamxe2x80x9d]. Because of the low density of the foam material, both the device for the fixing and also the medical-technical measuring device are of low mass. The longitudinal opening can be a blind hole or a through-passage opening and can be arranged in the center or eccentrically in relation to the longitudinal axis of the carrier means. Preferably, in any case, the axis of the longitudinal opening extends parallel to the axis of the carrier means. The diameter of the longitudinal opening is preferably somewhat smaller than the diameter of the smallest body part to which the measuring device is to be affixed.
The foam material or the entire carrier means can be manufactured of a semifinished material by stamping or cutting, particularly with use of a water stream or a laser beam. Thus, both the density and the cell dimensions of the foam material, as well as the material of the foam itself, can be adapted optimally to the relevant particular use being proposed. Generally speaking, such manufactured foam material parts or carrier means have neither blind holes nor any structures deviating from a cylindrical shape.
With the foam material part having incisions originating from the longitudinal opening and extending at least some distance in the longitudinal direction, at least two segments are formed by the incisions around the periphery, and extend in peripheral direction. Potential tensile stresses generate a deformation such that disturbing the measuring method is prevented. The number of incisions and the number of segments formed by the incisions can be adapted to the dimensions and configuration of the body part.
The incisions extend radially through at least half of the thickness of the foam part. An appreciable compensation for the deformation of one segment is then guaranteed by the deformation of an adjacent segment. Thus a permanently reliable and tight contact of the foam material on the body part is guaranteed.
The segments are connected with one another on their exterior by a layer of foam material configured of one single piece with the segments. The exterior shape of the carrier means during introduction of the body part or while the arrangement is being slipped over a body part is then not varied noticeably. Optimum contact of the foam material on the body part is guaranteed on all sides. For example, in the case of a measuring device with optical electronic measuring means, when the body part is displaced or turned over, the light is reliably prevented from getting to the receiver either directly from the transmitter or through reflection. This feature can be attained either alternatively or as a supplement by the foam material being colored with a dye. The dye is adapted to an optical electronic measurement to be carried out by the measuring device. Particularly, the radiation originating from a transmitter element is essentially completely absorbed.
The permanently secure fixing is further improved by the shape of the longitudinal opening being designed to be the shape of the body part which will receive it. For example, the longitudinal opening to receive a finger or a toe can be configured in conical shape with at least two padding pieces or beads. The padding pieces or beads are arranged one behind the other in the direction of the longitudinal layout, separated from one another by a narrowed section and rounded either inward or outward.
The carrier means has a transverse opening into which the measuring means is to be inserted, particularly on opposite sides of the body part. A secure and, if necessary, detachable mounting of the measuring means and an exact axial alignment of one to the other are then guaranteed. By such detachable mounting of the measuring means, the carrier means can be exchanged simply and at low cost if it becomes necessary, for instance for hygienic requirements.
A connection to the measuring means can be attached to a point on the exterior of the carrier means. The arrangement for fixing to a body part and the associated measuring device are then simple to manage and operate. Furthermore, fatiguing bending stresses of the connecting line and the connection points are particularly avoided, whereupon the operation and maintenance costs of the measuring device are also lowered considerably. The mounting can be executed by catch devices configured, for example, of one piece and mounted on the exterior.
On its exterior side more distant from the body part, the carrier means can have a rigid casing around the foam material. The stability of the exterior shape of the carrier means as well as a sufficient level of fixing force are then guaranteed. The casing, for example, can be formed by a sheathing of plastic or metal. Alternatively or as a supplement, an integral or structural foam material with solid skin and cellular core, all of one piece can be formed. The exchangeability of the foam material is further simplified when the sheathing is of a plurality of parts, particularly when it can be opened for the introduction of the foam material. For example, the sheathing can have an articulation-like device so that it can be opened, which device is configured preferably of one or more of the sheathing parts integrated into one piece.
The present invention also relates to a medical-technical measuring device for measuring physiological data of a patient, particularly a pulsoximeter sensor, with a fixing arrangement as described above. The measuring device has optical electronic measuring means arranged on the carrier means. A measuring procedure yielding reliable physiological data is then guaranteed by using a measuring device configured according to the present invention. In addition, the measuring device according to the present invention is of low cost to manufacture and maintain, as well as being simple to use.
The measuring means can include at least one optical transmitter element and at least one optical receiver element. The elements are arranged along the same axis through a transverse opening on opposite sides of the carrier means. The axial alignment of transmitter and receiver elements is guaranteed even under the mechanical stress of the arrangement for the fixing, for example, during introduction of the body part or during slipping of the arrangement over the body part. The foam material of the carrier means is essentially impermeable for the radiation emitted from the optical electronic measuring means. Particularly, it can be tinted with a corresponding suitable dye. In this manner, erroneous measurements, occurring for example because of reflections of the emitted radiation on the foam material, are essentially excluded from occurring.